Method for the manufacture of hardened railroad rails

Details Method for the manufacture of hardened railroad rails Method for the manufacture of hardened railroad rails

1988-08-19

1990-01-23

Yee, Deborah

Metal treatment

Compositions

Heat treating

148 124, 148 12B, 148146, C21D 904

Patent

active

048956058

ABSTRACT:
An improved method for the manufacture of hardened railroad rails comprises the steps of forming a railroad rail from an alloy steel of a preselected chemical composition, force cooling the rail from a preselected cooling start temperature above about the austenite-to-ferrite transformation temperature, terminating the force cooling when the temperature of rail reaches a preselected cooling stop temperature, and before a substantial volume fraction of the austenite in the rail head has transformed to pearlite, and holding the rail under substantially isothermal conditions until the austenite-to-pearlite transformation is complete. The chemical composition of the alloy steel is selected such that the austenite-to-pearlite reaction occurs earlier in time than the austenite-to-bainite reaction under the substantially isothermal conditions. The use of this method makes avoidance of bainite easier to achieve, so relatively simple and inexpensive process control equipment can be utilized.

REFERENCES:
patent: 4375995 (1983-03-01), Sugino et al.
patent: 4426236 (1984-01-01), Sugino et al.
patent: 4486248 (1984-12-01), Ackert et al.
patent: 4668308 (1987-05-01), Economopoulos et al.
patent: 4714500 (1987-12-01), Heller et al.
Effects of Manganese, Chromium, and Molybdenum on the Isothermal Transformation of Austenite in Eutectoid Steels by Y. S. Park and F. B. Fletcher, 1986 American Society for Metals, vol. 4, No. 3, Jun. 1986, pp. 247-252.

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